Herweg Nora A, Apitz Thore, Leicht Gregor, Mulert Christioph, Fuentemilla Lluís, Bunzeck Nico
Department of Systems Neuroscience and
Department of Systems Neuroscience and.
J Neurosci. 2016 Mar 23;36(12):3579-87. doi: 10.1523/JNEUROSCI.3629-15.2016.
Recollection of contextual information represents the core of human recognition memory. It has been associated with theta (4-8 Hz) power in electrophysiological recordings and, independently, with BOLD effects in a network including the hippocampus and frontal cortex. Although the notion of the hippocampus coordinating neocortical activity by synchronization in the theta range is common among theoretical models of recollection, direct evidence supporting this hypothesis is scarce. To address this apparent gap in our understanding of memory processes, we combined EEG and fMRI during a remember/know recognition task. We can show that recollection-specific theta-alpha (4-13 Hz) effects are correlated with increases in hippocampal connectivity with the PFC and, importantly, the striatum, areas that have been linked repeatedly to retrieval success. Together, our results provide compelling evidence that low-frequency oscillations in the theta and alpha range provide a mechanism to functionally bind the hippocampus, PFC, and striatum during successful recollection.
Low-frequency oscillations are supposed to drive the binding of information across a large-scale network centered on the hippocampus, which supports mnemonic functions. The electrophysiological means to investigate this phenomenon in humans (EEG/MEG), however, are inherently limited by their spatial resolution and therefore do not allow a precise localization of the brain regions involved. By combining EEG with BOLD-derived estimates of hippocampal connectivity during recognition, we can identify the striatum and specific areas in the medial and lateral PFC as part of a circuit linked to low-frequency oscillations (4-13 Hz) that promotes hippocampus-dependent context retrieval. Therefore, the current study closes an apparent gap in our understanding of the network dynamics of memory retrieval.
情境信息的回忆是人类识别记忆的核心。在电生理记录中，它与theta（4 - 8赫兹）功率相关，并且独立地与包括海马体和额叶皮质在内的网络中的血氧水平依赖（BOLD）效应相关。尽管在回忆的理论模型中，海马体通过theta范围内的同步来协调新皮质活动的观点很常见，但支持这一假设的直接证据却很少。为了填补我们在记忆过程理解上的这一明显空白，我们在一个记得/知道识别任务中结合了脑电图（EEG）和功能磁共振成像（fMRI）。我们能够表明，特定于回忆的theta - alpha（4 - 13赫兹）效应与海马体与前额叶皮质（PFC）以及重要的纹状体之间连接性的增加相关，这些区域反复与检索成功相关联。总之，我们的结果提供了令人信服的证据，即theta和alpha范围内的低频振荡在成功回忆期间提供了一种机制，以功能性地连接海马体、PFC和纹状体。
低频振荡被认为驱动以海马体为中心的大规模网络中信息的绑定，这支持记忆功能。然而，在人类中研究这一现象的电生理手段（脑电图/脑磁图）在空间分辨率上存在固有局限性，因此不允许对所涉及的脑区进行精确的定位。通过在识别过程中将脑电图与基于血氧水平依赖的海马体连接性估计相结合，我们可以确定纹状体以及内侧和外侧PFC中的特定区域是与促进海马体依赖的情境检索的低频振荡（4 - 13赫兹）相关电路的一部分。因此，当前的研究填补了我们在记忆检索网络动力学理解上的一个明显空白。
